Overhang isolation technology

Details Overhang isolation technology Overhang isolation technology

1987-03-24

1988-07-05

Chaudhuri, Olik

Fishing, trapping, and vermin destroying

437 62, 437 64, 437 73, 437 80, 437228, H01L 21467, H01L 21473, H01L 21475, H01L 2176

Patent

active

047554770

ABSTRACT:
A process for defining isolation structures between active regions of an integrated circuit is disclosed. The technique includes first forming a thermally grown silicon dioxide layer. A polysilicon layer is then deposited over the silicon dioxide layer and a silicon nitride-I layer is deposited thereon. A photo-resist mask is then formed on the top of the laminate and selective anisotropic dry etching is used to remove the unmasked silicon nitride-I and polysilicon layers. This step is followed by an isotropic dry etching to undercut the polysilicon beneath the silicon nitride-I layer. After the photo-resist masks and unmasked pad oxide are removed, a layer of silicon nitride-II is deposited. Thereafter, an anisotropic dry etching step is performed to remove the unmasked silicon nitride-II completely. An implantation step is then optionally performed. The uncovered silicon substrate is oxidized to form the isolation regions and, finally, the residual layers of silicon nitride-I, -II, polysilicon and pad oxide are removed. The silicon nitride-I and -II layers may be removed with boiling H.sub.3 PO.sub.4, the polysilicon layer by using reactive-ion etching, and the pad oxide layer by using 50:1 hydrogen fluoride.

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